This invention relates to a steering wheel mounted on a body of a motor vehicle and having an impact energy absorbing member.
In a conventional steering wheel, an impact energy absorbing member is disposed between a pad placed in the highest position in a central boss assembly of the steering wheel and a group of other boss assembly members, i.e., a boss connected to a steering shaft and a boss core formed of a metallic plate. Known impact energy absorbing members for this kind of use include a metallic plate having a generally U-shaped cross-section open at its bottom and a tubular member formed of a brittle plastic such as hard foamed urethane (e.g., those disclosed in Japanese Utility Model Unexamined Publication Nos. 1-158374 and 1-68635).
When an impact force is applied to an impact energy absorbing member from above, it is plastically deformed if it is formed of a metallic plate, or is deformed by brittle fracture if it is formed of a brittle plastic. The member is deformed to absorb the impact energy by reducing its size generally in the axial direction of the steering shaft.
The conventional impact energy absorbing member is therefore arranged to be attached to the steering wheel body at a lower position such as to avoid obstruction to its deformation, i.e., to enable a reduction in height when an impact force is applied thereto from above.
In steering wheels using the conventional impact energy absorbing member, a pad for convering the impact energy absorbing member is disposed above the impact energy absorbing member and is attached to this member. That is, the pad is attached to the steering wheel body with the impact energy absorbing member interposed therebetween. It is therefore difficult to position the pad correctly on the steering wheel body with respect to an upper surface of a spoke covering layer provided on the steering wheel body.
To enable the pad to be positioned easily with respect to the upper surface of the spoke covering layer, the pad and the impact energy absorbing member may be assembled in such a manner that the impact energy absorbing member is attached to a portion of the steering wheel body in the vicinity of the upper surface of the spoke covering layer, and the pad is attached to a portion of the impact energy absorbing member in the vicinity of the upper surface of the spoke covering layer.
In this type of steering wheel, however, an upper surface of the pad is positioned so as to be generally flush with a formed surface of a steering wheel ring and not to protrude beyond this surface, and the upper surface of the spoke covering layer is formed so as to be generally flush with the upper surface of the pad.
For this reason, the impact energy absorbing member is attached, by utilizing a portion in the vicinity of the upper surface of the spoke covering layer, to the steering wheel body by its upper portion.
If the impact energy absorbing member is attached to the steering wheel body by its upper portion, it is difficult for the impact energy absorbing member to have its specific property, i.e., a capability to be deformed so as to be reduced in height when an impact force is applied thereto.
In view of the above-described problems, an object of the present invention is to provide a steering wheel having an impact energy absorbing member capable of absorbing a predetermined amount of impact energy while being attached in a predetermined position to the steering wheel through its upper portion.